add header-only prometheus lib to ext

ext/prometheus-cpp-lite-1.0/examples/use_gauge_in_class_example.cpp

@@ -0,0 +1,79 @@
+#include <prometheus/registry.h>
+#include <prometheus/gauge.h>
+#include <prometheus/text_serializer.h>
+
+#include <array>
+#include <chrono>
+#include <cstdlib>
+#include <memory>
+#include <string>
+#include <thread>
+#include <iostream>
+
+// use prometheus namespace
+using namespace prometheus;
+
+// for clarity, we deduce the required types
+using IntegerGauge  = Gauge<int64_t>;
+using FloatingGauge = Gauge<double>;
+
+using IntegerGaugeFamily  = CustomFamily<IntegerGauge>;
+using FloatingGaugeFamily = CustomFamily<FloatingGauge>;
+
+// create global registry for use it from our classes
+static Registry globalRegistry;
+
+class MyClass {
+
+  IntegerGaugeFamily& gaugeFamily1  { IntegerGauge::Family::Build(globalRegistry,
+                                      "gauge_family_1", "gauge for check integer functionality",
+                                      {{"type","integer"}} ) };
+  
+  IntegerGauge& gauge11{ gaugeFamily1.Add({{"number", "1"}}) };
+  IntegerGauge& gauge12{ gaugeFamily1.Add({{"number", "2"}}) };
+  IntegerGauge& gauge13{ gaugeFamily1.Add({{"number", "3"}}) };
+  
+  
+  FloatingGaugeFamily& gaugeFamily2 { FloatingGauge::Family::Build(globalRegistry,
+                                      "gauge_family_2", "gauge for check floating functionality",
+                                      {{"type","float"}} ) };
+  
+  FloatingGauge& gauge21{ gaugeFamily2.Add({{"number", "1"}}) };
+  FloatingGauge& gauge22{ gaugeFamily2.Add({{"number", "2"}}) };
+  FloatingGauge& gauge23{ gaugeFamily2.Add({{"number", "3"}}) };
+
+public:
+
+  MyClass() = default;
+
+  void member_to_do_something() {
+
+    const int random_value = std::rand();
+
+    if (random_value &  1      ) gauge11++; else gauge11--;
+    if (random_value & (1 << 1)) gauge12++; else gauge12--;
+    if (random_value & (1 << 2)) gauge13++; else gauge13--;
+    if (random_value & (1 << 3)) gauge21++; else gauge21--;
+    if (random_value & (1 << 4)) gauge22++; else gauge22--;
+    if (random_value & (1 << 5)) gauge23++; else gauge23--;
+
+  }
+
+};
+
+int main() {
+
+  MyClass myClass;
+
+  for (;; ) {
+
+    std::this_thread::sleep_for(std::chrono::seconds(1));
+
+    myClass.member_to_do_something();
+
+    TextSerializer text_serializer;
+    text_serializer.Serialize(std::cout, globalRegistry.Collect());
+
+  }
+}
+